Total or partial deafnesses are now being treated by putting a cochlea implant into place in the cochlea, and more precisely an electrode carrier carrying an array of electrodes and connected to a receiver/stimulator that is implanted in the patient's skull.
The conventional technique for implanting a cochlea consists in performing mastoidectomy by removing the mastoid bone that projects behind the pinna. Then a narrow passage between the facial nerve and the external auditory canal is provided by means of a posterior tympanotomy. Finally, a cochleostomy gives access to the inside of the cochlea in order to enable the electrode carrier to be put into place in the cochlea. That technique is considered as being very invasive.
Recent proposals have been made to perform such operations with the help of a surgical assistance robot, the robot being guided by means of navigation algorithms based on preoperative or peroperative images, e.g. obtained with a scanner. In particular, the robot has an arm, the end of which is provided with a drilling tool (such as a drill bit) for drilling an access passage to the entry of the cochlea through the mastoid bone. Such techniques are considerably less invasive.
Nevertheless, the accuracy of such navigation (which accuracy is of millimeter order) is not good enough to be sure of making a passage through the mastoid bone without running the risk of injuring the facial nerve. This nerve is situated on the approach path for posterior tympanotomy.